High Dietary Acid Load Predicts ESRD

ATLANTA—Higher dietary acid load is associated with an increased likelihood of chronic kidney disease (CKD) progression, according to two new studies presented at Kidney Week 2013.

In a study of 1,486 adults with CKD who participated in the National Health and Nutrition Examination Survey III, Tanushree Banerjee, PhD, of the University of California San Francisco, and colleagues demonstated that higher dietary acid load is associated with development of end-stage renal disease (ESRD) among CKD patients.

This is the first longitudinal study on the association of dietary acid load and progression to ESRD in a nationally representative cohort. ESRD developed in 311 participants (20.9%) during a median of 14.2 years of follow-up. Compared with subjects in the lowest tertile of net acid excretion (NAE), those in the middle and highest tertiles had a 3.8 times and 8.6 times increased risk for ESRD. For the study, the investigations ascertained NAE by 24-hr dietary recall questionnaire.

The risk associated with elevated NAE increased in a graded fashion with estimated glomerular filtration rate (eGFR). Among subjects with an eGFR below 45 mL/min/1.73 m2, those in the middle and highest tertiles of NAE had a significant 9.4 and 13.8 times increased risk of ESRD compared with participants in the lowest tertile. Among participants with an eGFR of 45 and higher, those in the middle and highest tertiles of NAE had a significant 5.7 and 7.6 times increased risk compared with subjects in the lowest tertile.

Furthermore, among subjects with albuminuria (30 mg/g or higher), those in the middle and highest NAE tertiles had a significant 15% and 6.5 times increased risk of ESRD compared with subjects in the lowest tertile. In participants without albuminuria, NAE was not significantly associated with ESRD risk. In a fully adjusted model, each 25 mEq/day increment in NAE was associated with a 2.4 times increased risk of ESRD.

In the other study, a Japanese team found that high net endogenous acid production (NEAP) is associated with CKD progression. The primary endpoint of their study, which included 249 elderly CKD patients (average age 70.6 years), was a 25% decline in eGFR or initiating dialysis.

In adjusted analyses, patients in the upper half of the NEAP range had a nearly twofold increased risk for CKD progression compared with NEAP levels in the lower half of the range, Eiichiro Kanda, MD, of Tokyo Kyosai Hospital, and colleagues reported.